This invention relates to aryl-substituted-bridge containing organometallic catalyst compounds suitable for olefin polymerization processes.
Olefin polymers comprising ethylene and at least one or more xcex1-olefin and optionally one or more diolefin make up a large segment of polyolefin polymers and will be addressed as xe2x80x9cethylene copolymersxe2x80x9d herein. Such polymers range from crystalline polyethylene copolymers such as High Density Polyethylene with a density in excess of 0.94, to slightly crystalline polyethylene such as Linear Low Density Polyethylene with a density between 0.915 to 0.94, to largely amorphous elastomers with a density down to 0.85 and a relatively high molecular weight and with a new area of semi-crystalline xe2x80x9cplastomersxe2x80x9d with a density of between 0.915 and 0.86 and a moderate molecular weight. In particular, ethylene copolymer plastomers are now a well established class of industrial polymers having a variety of uses associated with their unique properties, such as elastomeric properties and their thermo-oxidative stability. Uses of the plastomers include general thermoplastic olefins, films, wire and cable coatings, polymer modification, injection molding, foams, footwear, sheeting, functionalized polymers and components in adhesive and sealant compounds.
Commercially prepared ethylene copolymers have been traditionally been made via Ziegler-Natta polymerization with catalyst systems largely based on vanadium or titanium. Newer metallocene catalyst compounds have received attention due to their ease of larger monomer incorporation and potential increases in polymerization activities. U.S. Pat. No. 5,324,800 describes metallocenes having substituted and unsubstituted cyclopentadienyl ligands which are suitable for producing high molecular weight olefin polymers, including linear, low density copolymers of ethylene with minor amounts of xcex1-olefin.
The utility of bridged metallocene-based ionic catalysts in olefin polymerization is described in U.S. Pat. Nos. 5,408,017 and 5,767,208, EP 0 612 768, and EP 0 612 769. Each addresses suitable bridged metallocene catalysts for high temperature processes for olefin copolymerization. Substituted single carbon, or methylene, bridging groups for metallocenes suitable as olefin polymerization catalysts is described in U.S. Pat. Nos. 4,892,851, 5,155,080 and 5,132,381. Isopropylidene, mono- and diaryl methylene groups are identified as particularly suitable.
Olefin solution polymerization processes are generally conducted in aliphatic solvents that serve both to maintain reaction medium temperature profiles and solvate the polymer products prepared. However, aryl-group containing metallocenes, those having cyclopentadienyl derivatives and other fused or pendant aryl-group substituents, are at best sparingly soluble in such solvents and typically are introduced in aryl solvents such as toluene. Solution polymerization processes in aliphatic solvents thus can be contaminated with toluene that must be removed to maintain process efficiencies and to accommodate health-related concerns for both industrial manufacturing processes and polymer products from them. Alternatively, relatively insoluble catalysts can be introduced via slurry methods, but such methods required specialized handling and pumping procedures that complicate and add significant costs to industrial scale plant design and operation. Low solubility can also become disadvantageous should the process involve low temperature operation at some stage such as in typical adiabatic processes run in areas subject to low ambients temperatures. Additionally, separating or counteracting the build up in the recycle system of special catalyst solvents may become another problem. At the same time means of maintaining high molecular weights in olefin polymers while operating at economically preferable high polymerization reaction temperatures and high polymer production rates is highly desirable. It is therefore desirable to provide a metallocene catalyst which is active for polyethylene polymerization particularly at elevated temperatures which nevertheless has increased solubility in aliphatic solvents.
The invention thus addresses specifically substituted, bridged metallocene catalyst complexes comprising a solubilizing covalent bridge comprising at least one hydrocarbylsilyl substitutent. It can be described as a Group 4 organometallic compound comprising two ancillary monanionic ligands, each of which independently may be substituted or unsubstituted, wherein the ligands are bonded by a covalent bridge containing a substituted single Group 14 atom, the substitution on said Group 14 atom comprising aryl groups at least one of which contains at least one hydrocarbylsilyl substituent group sufficient to provide increased solubility in aliphatic solvents. Additionally, the invention relates to solution polymerization processes for ethylene copolymers having a density of about 0.850 to about 0.940 comprising contacting, under supercritical or solution polymerization conditions at reaction temperatures of 40xc2x0 C. to 300xc2x0 C., ethylene and one or more comonomers capable of insertion polymerization with a metallocene catalyst complex derived from A) a metallocene compound having a covalent bridge connecting a cyclopentadienyl ligand to another ancillary anionic metal ligand group, said bridge containing a substituted single Group 14 atom, the substitution on said Group 14 comprising aryl groups at least one of which contains at least one hydrocarbylsilyl substituent group of the formula R2nSiR13xe2x88x92n, where each R1 is independently a C1-C20 hydrocarbyl, hydrocarbylsilyl, hydrofluorocarbyl substitutent, R2 is a C1-C10 linking group between Si and the aryl group, and n=0, 1 or 2. Where n=0, the Si atom is covalently bound directly to an aryl group ring carbon atom.
The bridged metallocene compounds of the invention are those having a single substituted carbon or silicon atom bridging two ancillary monanionic ligands, such as substituted or unsubstituted cyclopentadienyl-containing (Cp) ligands and/or substituted and unsubstituted Group 13-16 heteroatom ligands, of the metallocene metal centers. The bridge substituents are substituted aryl groups, the substituents including at least one solubilizing hydrocarbylsilyl substituent located on at least one of the aryl group bridge substituents. Substituents present on the cyclopentadienyl and/or heteroatom ligands include C1-C30 hydrocarbyl, hydrocarbylsilyl or hydrofluorocarbyl groups as replacements for one or more of the hydrogen groups on those ligands, or those on fused aromatic rings on the cyclopentadienyl rings. Aromatic rings can be substituents on cyclopentadienyl ligand and are inclusive of the indenyl and fluorenyl derivatives of cyclopentadienyl groups, and their hydrogenated counterparts. Such typically may include one or more aromatic ring substituent selected from linear, branched, cyclic, aliphatic, aromatic or combined structure groups, including fused-ring or pendant configurations. Examples include methyl, isopropyl, n-propyl, n-butyl, isobutyl, tertiary butyl, neopentyl, phenyl, n-hexyl, cyclohexyl, benzyl, and adamantyl. For the purposes of this application the term xe2x80x9chydrocarbonxe2x80x9d or xe2x80x9chydrocarbylxe2x80x9d is meant to include those compounds or groups that have essentially hydrocarbon characteristics but optionally contain not more than about 10 mol. % non-carbon heteroatoms, such as boron, silicon, oxygen, nitrogen, sulfur and phosphorous. Additionally, the term is meant to include hydrofluorocarbyl substitutent groups. xe2x80x9cHydrocarbylsilylxe2x80x9d is exemplified by, but not limited to, dihydrocarbyl- and trihydrocarbylsilyls, where the preferred hydrocarbyl groups are preferably C1-C30 substituent hydrocarbyl, hydrocarbylsilyl or hydrofluorocarbyl substitutents for the bridging group phenyls. For heteroatom containing catalysts see WO 92/00333. Also, the use of hetero-atom containing rings or fused rings, where a non-carbon Group 13, 14, 15 or 16 atom replaces one of the ring carbons is considered for this specification to be within the terms xe2x80x9ccyclopentadienylxe2x80x9d, xe2x80x9cindenylxe2x80x9d, and xe2x80x9cfluorenylxe2x80x9d. See, for example, the background and teachings of WO 98/37106, having common priority with U.S. Ser. No. 08/999,214, filed Dec. 29, 1997, and WO 98/41530, having common priority with U.S. Ser. No. 09/042,378, filed Mar. 13, 1998, both incorporated by reference for purposes of U.S. patent practice.
These compounds can be generically represented as illustrated below: 
where Cp is a substituted or unsubstituted cyclopentadienyl-containing ancillary ligand, L is independently selected from Cp ligands as previously defined, or is a substituted or unsubstituted Group 13-16 heteroatom ligand, T is a Group 14 element-containing bridging group, AR1 and Ar2 are the substituted aryl groups which may be the same or different, M is a Group 3-6 metal, and X1 and X2 are the same or different labile ligands capable of being abstracted for activation and suitable for olefin insertion, or capable of alkylation so as to be abstractable and suitable for olefin insertion. The term xe2x80x9cancillary ligandxe2x80x9d is being used to refer to bulky monoanioic ligands that stabilize the metal center to which bonded against oxidative reaction (i.e., debonding of the ligand by chemical reaction) and the term xe2x80x9clabile ligandxe2x80x9d refers to ligands which may be readily replaced, abstracted, or removed from the metal center to which bonded.
For illustration purposes Ar1 and Ar2 may be independently selected from the groups below: 
where any Rxe2x80x2 is independently any of the groups below except H and any Rxe2x80x2xe2x80x3 is independently any of the groups below:
Cp and L, independently, may be any of ligands below where Rxe2x80x2xe2x80x3 is as shown above. 
X1 and X2 may independently be any of the groups listed for Rxe2x80x2xe2x80x3 plus any of Cl, Br, I, xe2x80x94NHRxe2x80x2xe2x80x3, xe2x80x94N(Rxe2x80x2xe2x80x3)2, or xe2x80x94ORxe2x80x2xe2x80x3. X1 and X2 may additionally be linked together so as to form a bidentate ligand such as cycloaliphatic hydrocarbyl bidentate ligand or cycloalkenyl hydrocarbyl ligand.
An illustrative representative is 
where Me is methyl, Et is ethyl and Octyl is octyl.
Specific exemplary bridged hafnium catalysts include those derived from: indenyl-based complexes such as the isomers, or mixtures, of di(para-triethylsilyl-phenyl)methylene bis(indenyl) hafnium dimethyl, di(para-trimethylsilyl-phenyl)methylene bis(indenyl) hafnium dimethyl, of di(para-tri-n-propylsilyl-phenyl)methylene bis(indenyl)hafnium dimethyl, (para-triethylsilyl-phenyl)(para-t-butylphenyl)methylene(fluorenyl) (indenyl) hafnium dimethyl, (para-triethylsilyl-phenyl)(para-methylphenyl)methylene (fluorenyl)(indenyl)hafnium dimethyl, di(para-triethylsilyl-phenyl)methylene(2,7-di tertbutyl fluorenyl)(indenyl)hafnium dimethyl, (para-trimethylsilyl-phenyl)(para-n-butylphenyl)methylene (2,7-di tertbutyl fluorenyl)(indenyl) hafnium dimethyl, (para-triethylsilyl-phenyl) (para-n-butylphenyl)methylene bis(tetrahydroindenyl)hafnium dibenzyl and di(para-triethylsilyl-phenyl)methylene bis(tetrahydroindenyl)hafnium dimethyl.
Similarly, exemplary zirconium compounds include di(para-triethylsilyl-phenyl)methylene bis(indenyl)zirconium dimethyl, di(para-trimethylsilyl-phenyl)methylene bis(indenyl)zirconium dimethyl, of di(para-tri-n-propylsilyl-phenyl)methylene bis(indenyl)zirconium dimethyl, (para-triethylsilyl-phenyl)(para-t-butylphenyl)methylene(fluorenyl) (indenyl)zirconium dimethyl, (para-triethylsilyl-phenyl)(para-methylphenyl)methylene (fluorenyl)(indenyl)zirconium dimethyl, di(para-triethylsilyl-phenyl)methylene(2,7-di tertbutyl fluorenyl)(indenyl)zirconium dimethyl, (para-trimethylsilyl-phenyl)(para-n-butylphenyl)methylene (2,7-di tertbutyl fluorenyl)(indenyl)zirconium dimethyl, (para-triethylsilyl-phenyl) (para-n-butylphenyl)methylene bis(tetrahydroindenyl)zirconium dibenzyl and di(para-triethylsilyl-phenyl)methylene bis(tetrahydroindenyl)zirconium dimethyl. Additional preferred zirconium metallocenes useful when prepared with the solubilizing bridging groups in accordance with this invention are those described in copending U.S. application Ser. No. 09/251,819, filed Feb. 17, 1999, and equivalent WO 99/41294, these catalyst structures and the solution polymerization process described with them are particularly suited for this invention, and are incorporated by reference for purposes of U.S. patent practice.
Particularly suitable cyclopentadienyl-based complexes are the compounds, isomers, or mixtures, of (para-trimethylsilylphenyl)(para-n-butylphenyl)methylene(fluorenyl)(cyclopentadienyl)hafnium dimethyl, di(para-trimethylsilylphenyl)methylene(2,7-di-tertbutyl fluorenyl)(cyclopentadienyl)hafnium dimethyl, di(para-trimethylsilylphenyl)methylene(2,7-di-tertbutyl-fluorenyl)(cyclopentadienyl)hafnium dimethyl, (para-trimethylsilylphenyl)(para-t-butylphenyl)methylene(2,7-di tertbutyl fluorenyl)(cyclopentadienyl)hafnium dimethyl or dibenzyl, and di(para-trimethylsilylphenyl)methylene(2,7-dimethylfluorenyl)(cyclopentadienyl)hafnium dimethyl or dibenzyl. The zirconocene analogues are (para-trimethylsilylphenyl)(para-n-butylphenyl)methylene(fluorenyl)(cyclopentadienyl)zirconium dimethyl, di(para-trimethylsilylphenyl)methylene(2,7-di-tertbutyl fluorenyl)(cyclopentadienyl)zirconium dimethyl, di(para-trimethylsilylphenyl)methylene(2,7-di-tertbutyl-fluorenyl)(cyclopentadienyl)zirconium dimethyl, (para-trimethylsilylphenyl)(para-t-butylphenyl)methylene(2,7-di tertbutyl fluorenyl)(cyclopentadienyl)zirconium dimethyl or dibenzyl, and di(para-triethylsilyl-phenyl)methylene(2,7-dimethylfluorenyl)(cyclopentadienyl)zirconium dimethyl or dibenzyl. It has been found that the substituted bridge-containing compounds, such as those asymmetric compounds listed above, are particularly useful in accordance with the invention.
In particular, for the bridged metallocene compounds, increasing the degree of substitution on an aromatic fused-ring substituted ligand Cp can be effective for increased molecular weight, e.g., 2,7-dimethyl-fluorenyl, 2,7-di-tert-butyl-fluorenyl and 2,7-methyl-phenyl-fluorenyl groups are exemplary of such. Preferably substitution on fluorenyl or indenyl radicals (ii) in the metallocene compounds will generally comprise two or more C1 to C30 hydrocarbyl or hydrocarbylsilyl replacements, or substitutions, for a ring hydrogen of at least one 6-member fused-ring, preferably both where a fluorenyl radical.
The bridged metallocene compounds according to the invention may be activated for polymerization catalysis in any manner sufficient to allow coordination or cationic polymerization. This can be achieved for coordination polymerization when one ligand can be abstracted and another will either allow insertion of the unsaturated monomers or will be similarly abstractable for replacement with a ligand that allows insertion of the unsaturated monomer (labile ligands), e.g., alkyl, silyl, or hydride. The traditional activators of coordination polymerization art are suitable, those typically include Lewis acids such as alumoxane compounds, and ionizing, anion precursor compounds that abstract one so as to ionize the bridged metallocene metal center into a cation and provide a counter-balancing noncoordinating anion.
Alkylalumoxanes and modified alkylalumoxanes are suitable as catalyst activators, particularly for the invention metal compounds comprising halide ligands. The alumoxane component useful as catalyst activator typically is an oligomeric aluminum compound represented by the general formula (Rxe2x80x3xe2x80x94Alxe2x80x94O)n, which is a cyclic compound, or Rxe2x80x3(Rxe2x80x3xe2x80x94Alxe2x80x94O)nAlRxe2x80x32, which is a linear compound. In the general alumoxane formula Rxe2x80x3 is independently a C1 to C10 alkyl radical, for example, methyl, ethyl, propyl, butyl or pentyl and xe2x80x9cnxe2x80x9d is an integer from 1 to about 50. Most preferably, Rxe2x80x3 is methyl and xe2x80x9cnxe2x80x9d is at least 4. Alumoxanes can be prepared by various procedures known in the art. For example, an aluminum alkyl may be treated with water dissolved in an inert organic solvent, or it may be contacted with a hydrated salt, such as hydrated copper sulfate suspended in an inert organic solvent, to yield an alumoxane. Generally, however prepared, the reaction of an aluminum alkyl with a limited amount of water yields a mixture of the linear and cyclic species of the alumoxane. Methylalumoxane and modified methylalumoxanes are preferred. For further descriptions see, U.S. Pat. Nos. 4,665,208, 4,952,540, 5,041,584, 5,091,352, 5,206,199, 5,204,419, 4,874,734, 4,924,018, 4,908,463, 4,968,827, 5,329,032, 5,248,801, 5,235,081, 5,157,137, 5,103,031 and EP 0 561 476 A1, EP 0 279 586 B1, EP 0 516 476 A, EP 0 594 218 A1 and WO 94/10180, each being incorporated by reference for purposes of U.S. patent practice.
When the activator is an alumoxane, the preferred transition metal compound to activator molar ratio is from 1:2000 to 10:1, more preferably from about 1:500 to 10:1, even more preferably from about 1:250 to 1:1 and most preferably from about 1:100 to 1:1.
The term xe2x80x9cnoncoordinating anionxe2x80x9d is recognized to mean an anion which either does not coordinate to the metal cation or which is only weakly coordinated to it thereby remaining sufficiently labile to be displaced by a neutral Lewis base, such as an olefinically or acetylenically unsaturated monomer. Any complex capable of counterbalancing a cationic charge without impeding or interfering with olefin polymerization, including both being incapable of reacting with metallocene cations so as to render them neutral and remaining sufficiently labile so as to be replaceable at the polymerization site by olefin monomers, will be suitable in accordance with the invention. Typically such complexes are based on ionic salts or neutral Lewis acids of the Group 8-14 metalloid or metal elements, particularly boron or aluminum having substituted aryl groups that are substituted so as to present steric or electronic impediments to oxidation of the complexes by reaction of the transition metal center with the aryl groups bonded to the Group 13 atoms. Zwitterionic complexes of Group 13 elements comprising both catonic and anionic charges where meeting the functional requisites above are additionally suitable.
Additional suitable anions are known in the art and will be suitable for use with the metallocene catalysts of the invention. See in particular, U.S. Pat. No. 5,278,119 and the review articles by S. H. Strauss, xe2x80x9cThe Search for Larger and More Weakly Coordinating Anionsxe2x80x9d, Chem. Rev., 93, 927-942 (1993) and C. A. Reed, xe2x80x9cCarboranes: A New Class of Weakly Coordinating Anions for Strong Electrophiles, Oxidants and Superacidsxe2x80x9d, Acc. Chem. Res., 31, 133-139 (1998).
Specific descriptions of ionic catalysts, those comprising a transition metal cation and a noncoordinating anion, suitable for coordination polymerization appear in the U.S. Pat. Nos. 5,064,802, 5,132,380, 5,198,401, 5,278,119, 5,321,106, 5,347,024, 5,408,017, 5,599,671, and international publications WO 92/00333, WO 93/14132 and WO 97/35893. These teach a preferred method of preparation wherein metallocenes are protonated by noncoordinating anion precursors such that an alkyl, alkenyl or hydride group is abstracted by protonation from a transition metal to make it both cationic and charge-balanced by the noncoordinating anion.
The use of ionizing ionic compounds not containing an active proton but capable of producing both the metallocene cation and an noncoordinating anion is also useful. See, EP-A-0 426 637, EP-A-0 573 403 and U.S. Pat. No. 5,387,568 for instructive ionic compounds. Reactive cations of the ionizing ionic compounds, other than the Bronsted acids, include ferrocenium, silver, tropylium, triphenylcarbenium and triethylsilylium, or alkali metal or alkaline earth metal cations such as sodium, magnesium or lithium cations. A further class of noncoordinating anion precursors suitable in accordance with this invention are hydrated salts comprising the alkali metal or alkaline earth metal cations and a non-coordinating anion as described above. The hydrated salts can be prepared by reaction of the metal cation-noncoordinating anion salt with water, for example, by hydrolysis of the commercially available or readily synthesized LiB(pfp)4 which yields [Li.xH2O][B(pfp)4], where (pfp) is pentafluorophenyl or perfluorophenyl.
Any metal or metalloid capable of forming a coordination complex which is resistant to degradation by water (or other Bronsted or Lewis Acids) may be used or contained in the noncoordinating anion. Suitable metals include, but are not limited to, aluminum, gold, platinum and the like. Suitable metalloids include, but are not limited to, boron, phosphorus, silicon and the like. The description of noncoordinating anions and precursors thereto of the documents of the foregoing paragraphs are incorporated by reference for purposes of U.S. patent practice.
An additional method of making the active polymerization catalysts of this invention uses ionizing anion pre-cursors which are initially neutral Lewis acids but form a metallocene cation and the noncoordinating anion upon ionizing reaction with the invention compounds, for example tris(pentafluorophenyl) boron acts to abstract a hydrocarbyl, hydride or silyl ligand to yield a metallocene cation and stabilizing noncoordinating anion, see EP-A-0 427 697 and EP-A-0 520 732 for illustration. See also the methods and compounds of EP-A-0 495 375. The description of noncoordinating anions and precursors thereto of these documents are similarly incorporated by reference for purposes of U.S. patent practice.
When the X1 and X2 labile ligands are not hydride, hydrocarbyl or silylhydrocarbyl, such as chloride, amido or alkoxy ligands and are not capable of discrete ionizing abstraction with the ionizing, anion pre-cursor compounds, these X ligands can be converted via known alkylation reactions with organometallic compounds such as lithium or aluminum hydrides or alkyls, alkylalumoxanes, Grignard reagents, etc. See EP-A-0 500 944, EP-A1-0 570 982 and EP-A1-0 612 768 for analogous processes describing the reaction of alkyl aluminum compounds with dihalide substituted metallocene compounds prior to or with the addition of activating noncoordinating anion precursor compounds.
Preferred invention activating cocatalyst, precursor ionizing compounds comprise Group 13 element complexes having at least two halogenated aromatic ligands such as the halogenated tetraphenyl boron and aluminum compounds exemplified in the identified prior art. Preferred aromatic ligands consist of the readily available phenyl, and polycyclic aromatic hydrocarbons and aromatic ring assemblies in which two or more rings (or fused ring systems) are joined directly to one another or together. These ligands, which may be the same or different, are covalently bonded directly to the metal/metalloid center. In a preferred embodiment the aryl groups are halogenated, preferably fluorinated, tetraaryl Group 13 element anionic complexes comprising at least one fused polycyclic aromatic hydrocarbon or pendant aromatic ring. The halogenated ligands are also represented by those aryl ligands having flourinated alkyl groups. Indenyl, napthyl, anthracyl, heptalenyl and biphenyl ligands are exemplary aryl ligands. See co-pending application U.S. Ser. No. 09/261,627, filed Mar. 3, 1999, and equivalent WO 99/45042, incorporated by reference for the purposes of U.S. patent practice.
Particularly preferred cocatalyst complexes for solution polymerization processes are those which are soluble in aliphatic solvents, whether by virtue of substitution on the Group 13 element ligands or substitution on precursor cations, see for example U.S. Pat. No. 5,502,017 and WO 97/35893. When the cation portion of an ionic noncoordinating anion precursor is a Bronsted acid such as protons or protonated Lewis bases (excluding water), or a reducible Lewis acid such as ferrocenium or silver cations, or alkaline metal or alkaline earth metal cations such as those of sodium, magnesium or lithium cations, the transition metal to activator molar ratio may be any ratio, but preferably from about 10:1 to 1:10, more preferably from about 5:1 to 1:5, even more preferably from about 2:1 to 1:2 and most preferably from about 1.2:1 to 1:1.2 with the ratio of about 1:1 being the most preferred.
Thus suitable active catalyst complexes for coordination and carbocationic polymerization can be prepared by activation with the traditional metallocene activators, typically alkylalumoxanes and ionizing haloaryl boron or aluminum compounds known in the art. The active catalysts thus are catalytically active components comprising complexes derived from the invention metallocene compounds containing the solubilizing bridge binding together the ancillary ligands according to the invention, and activating cocatalyst compounds.
The catalyst complexes of the invention are useful in polymerization of unsaturated monomers conventionally known to be polymerizable under either coordination polymerization conditions or cationic polymerization conditions. Such conditions are well known and include solution polymerization, supercritical phase polymerization, slurry polymerization, and low, medium and high pressure gas-phase polymerization. The catalyst of the invention may be supported and as such will be particularly useful in the known operating modes employing fixed-bed, moving-bed, fluid-bed, or slurry processes conducted in single, series or parallel reactors, with the added benefit that increased solubility will be useful in catalyst synthesis processes where the introduction of toluene is to be reduced or slurry pump introduction means to be avoided.
When using the catalysts of the invention, the total catalyst system will generally additionally comprise one or more organometallic compound. Such compounds as used in this application and its claims is meant to include those compounds effective for removing polar impurities from the reaction environment and for increasing catalyst activity. Impurities can be inadvertently introduced with any of the polymerization reaction components, particularly with solvent, monomer and catalyst feed, and adversely affect catalyst activity and stability. It can result in decreasing or even elimination of catalytic activity, particularly when ionizing anion pre-cursors activate the catalyst system. The polar impurities, or catalyst poisons include water, oxygen, metal impurities, etc. Preferably steps are taken before provision of such into the reaction vessel, for example by chemical treatment or careful separation techniques after or during the synthesis or preparation of the various components, but some minor amounts of organometallic compound will still normally be used in the polymerization process itself.
Typically these compounds will be organometallic compounds such as the Group 13 organometallic compounds of U.S. Pat. Nos. 5,153,157, 5,241,025 and WO-A-91/09882, WO-A-94/03506, WO-A-93/14132, and that of WO 95/07941. Exemplary compounds include triethyl aluminum, triethyl borane, triisobutyl aluminum, methylalumoxane, and isobutyl aluminumoxane. Those compounds having bulky or C6-C20 linear hydrocarbyl substituents covalently bound to the metal or metalloid center being preferred to minimize adverse interaction with the active catalyst. Examples include triethylaluminum, but more preferably, bulky compounds such as triisobutylaluminum, trisoprenylaluminum, and long-chain linear alkyl-substituted aluminum compounds, such as tri-n-hexylaluminum, tri-n-octylaluminum, or tri-n-dodecylaluminum. When alumoxane is used as activator, any excess over the amount needed to activate the catalysts present can act as a poison scavenger compound and additional organometallic compounds may not be necessary. Alumoxanes also may be used in scavenging amounts with other means of activation, e.g., methylalumoxane and trisobutyl-aluminoxane with boron-based activators. The amount of such compounds to be used with catalyst compounds of the inventions is minimized during polymerization reactions to that amount effective to enhance activity (and with that amount necessary for activation of the catalyst compounds if used in a dual role) since excess amounts may act as catalyst poisons.
In preferred embodiments of the process for this invention, the catalyst system is employed in liquid phase (solution, slurry, suspension, bulk phase or combinations thereof), in high pressure liquid or supercritical fluid phase. Each of these processes may be employed in singular, parallel or series reactors. The liquid processes comprise contacting olefin monomers with the above described catalyst system in a suitable diluent or solvent and allowing said monomers to react for a sufficient time to produce the invention copolymers. Aliphatic solvents and mixed aliphatic solvents are industrially suitable for solution processes, and are particularly preferred.
The process of the invention is especially applicable to homogeneous solution polymerization which is also substantially adiabatic, that is to say the heat of polymerization is accommodated by a rise in temperature of the polymerization reactor contents, here principally solvent. This adiabatic process typically has no internal cooling and suitably no external cooling. The reactor outlet stream removes the heat of polymerization from the reactor. The productivity of such adiabatic processes can be improved by cooling the inlet solvent and/or monomer stream(s) prior to introduction into the reactor to permit a greater polymerization exotherm. Thus the catalyst, cocatalyst and scavenger selections disclosed in this application can be advantageously practiced in a continuous, solution process operated at or above 140xc2x0 C., above 150xc2x0 C. or above 160xc2x0 C., up to about 250xc2x0 C. Typically this process is conducted in an inert hydrocarbon solvent, linear, cyclic or branched aliphatic, or aromatic, at a pressure of from 20 to 200 bar. These catalysts"" ability to provide a commercially desirable polymer at elevated temperatures contributes to a greater exotherm, to high polymer contents in the reactor because of lower viscosity, and to reduced energy consumption in evaporating and recycling solvent, and better monomer and comonomer conversions. See, for example, U.S. Pat. No. 5,767,208, and co-pending U.S. application Ser. No. 09/261,637, filed March 3, 1999, and its equivalent WO 99/45041, all of which are incorporated by reference for purposes of U.S. patent practice.
The catalyst according to the invention may be supported for use in gas phase, bulk, slurry polymerization processes, or otherwise as needed. Numerous methods of support are known in the art for copolymerization processes for olefins, any is suitable for the invention process in its broadest scope. See, for example, alumoxane activated catalysts of U.S. Pat. Nos. 5,057,475 and 5,227,440. An example of supported ionic catalysts appears in WO 94/03056. Particularly effective methods for ionic catalysts are that described in U.S. Pat. Nos. 5,427,991, 5,647,847 and WO 98/55518. A bulk, or slurry, process utilizing supported, invention metallocene compounds activated with alumoxane co-catalysts can be utilized as described for ethylene-propylene rubber in U.S. Pat. Nos. 5,001,205 and 5,229,478, these processes will additionally be suitable with the catalyst systems of this application. Both inorganic oxide and polymeric supports may be utilized in accordance with the knowledge in the field. See U.S. Pat. Nos. 5,422,325, 5,427,991, 5,498,582, 5,466,649, copending U.S. patent applications Ser. Nos. 08/265,532 and 08/265,533, both filed Jun. 24, 1995, and international publications WO 93/11172 and WO 94/07928. Each of the foregoing documents is incorporated by reference for purposes of U.S. patent practice.
Bulk and slurry processes are typically done by contacting the catalysts with a slurry of liquid monomer or diluent, the catalyst system being supported. Gas phase processes typically use a supported catalyst and are conducted in any manner known to be suitable for ethylene homopolymers or copolymers prepared by coordination polymerization. Illustrative examples may be found in U.S. Pat. Nos. 4,543,399, 4,588,790, 5,028,670, 5,382,638, 5,352,749, 5,436,304, 5,453,471, and 5,463,999, and WO 95/07942. Each is incorporated by reference for purposes of U.S. patent practice.
Generally speaking the polymerization reaction temperature can vary from about xe2x88x9250xc2x0 C. to about 300xc2x0 C. Preferably the reaction temperature conditions will be from xe2x88x9220xc2x0 C. to 250xc2x0, and most advantageously in high temperature, adiabatic solution processes from and including about 120xc2x0 C. to including and about 230xc2x0 C. The pressure can vary from about 1 mm Hg to 2500 bar, preferably from 0.1 bar to 1600 bar, most preferably from 1.0 to 500 bar.
Ethylene-xcex1-olefin (including ethylene-cyclic olefin and ethylene-xcex1-olefin-diolefin) elastomers of high molecular weight and low crystallinity can be prepared utilizing the catalysts of the invention under traditional solution polymerization processes (above) or by introducing ethylene gas into a slurry utilizing the xcex1-olefin or cyclic olefin or mixture thereof with other monomers, polymerizable and not, as a polymerization diluent in which the invention catalyst is suspended. Typical ethylene pressures will be between 10 and 1000 psig (69-6895 kPa) and the polymerization diluent temperature will typically be between xe2x88x9210-160xc2x0 C. The process can be carried out in a stirred tank reactor or tubular reactor, or more than one operated in series or parallel. See the general disclosure of U.S. Pat. No. 5,001,205 for general process conditions. All documents are incorporated by reference for description of polymerization processes, ionic activators and useful scavenging compounds.
Pre-polymerization of the supported catalyst of the invention may also be used for further control of polymer particle morphology in typical slurry or gas phase reaction processes in accordance with conventional teachings. For example such can be accomplished by pre-polymerizing a C2-C6 alpha-olefin for a limited time, for example, ethylene is contacted with the supported catalyst at a temperature of xe2x88x9215 to 30xc2x0 C. and ethylene pressure of up to about 250 psig (1724 kPa) for 75 min. to obtain a polymeric coating on the support of polyethylene of 30,000-150,000 molecular weight. The pre-polymerized catalyst is then available for use in the polymerization processes referred to above. The use of polymeric resins as a support coating may additionally be utilized, typically by suspending a solid support in dissolved resin of such material as polystyrene with subsequent separation and drying. All documents are incorporated by reference for description of metallocene compounds, ionic activators and useful scavenging compounds.
Other olefinically unsaturated monomers besides those specifically described above may be polymerized using the catalysts according to the invention by coordination polymerization, for example, styrene, alkyl-substituted styrenes, ethylidene norbornene, vinyl norbornene, norbornadiene, dicyclopentadiene, and other olefinically-unsaturated monomers, including other cyclic olefins, such as cyclopentene, norbornene, and alkyl-substituted norbornenes. Additionally, alpha-olefinic macromonomers of up to 300 mer units, or more, may also be incorporated by copolymerization.
The following examples are presented to illustrate the foregoing discussion. All parts, proportions and percentages are by weight unless otherwise indicated. All examples were carried out in dry, oxygen-free environments and solvents. Although the examples may be directed to certain embodiments of the present invention, they are not to be viewed as limiting the invention in any specific respect. In these examples certain abbreviations are used to facilitate the description. These include standard chemical abbreviations for the elements and certain commonly accepted abbreviations, such as Me=methyl, Et=ethyl, t-Bu=tertiary-butyl, Oct=octyl, Cp=cyclopentadienyl, Ind=indenyl, Flu=fluorenyl, THF (or thf)=tetrahydrofuran, Ph=phenyl, and pfp=pentafluorophenyl.
All molecular weights are weight average molecular weight unless otherwise noted. Molecular weights (weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by Gel Permeation Chromatography, unless otherwise noted, using a Waters 150 Gel Permeation Chromatograph equipped with a differential refractive index (DRI) and low angle light scattering (LS) detectors and calibrated using polystyrene standards. Samples were run in 1,2,4-trichlorobenzene (135xc2x0 C.) using three Polymer Laboratories PC Gel mixed B columns in series. This general technique is discussed in xe2x80x9cLiquid Chromatography of Polymers and Related Materials IIIxe2x80x9d J. Cazes Ed., Marcel Decker, 1981, page 207, which is incorporated by reference for purposes of U.S. patent practice herein. No corrections for column spreading were employed; however, data on generally accepted standards, e.g. National Bureau of Standards Polyethylene 1475, demonstrated a precision with 0.2 units for Mw/Mn which was calculated from elution times.